Electric and photoelectric properties of polycrystalline copper sulphide

Polycrystalline samples of copper sulphide having a predominantly tetragonal phase have been investigated. The thermal activation energy of the electric conductivity Delta E a =0.15 eV associated with the activation energy of an acceptor level has been determined. Low-temperature photoconductivity has been observed for the first time. The photoconductivity spectra measured at 80-120K reveal an appreciable surface recombination rate. From the analysis of these spectra, the minority carrier diffusion length (3.3*10 -5 -2.5*10 -4 cm) and the possible lower limit of the band gap ( Delta E g approximately=1.2 eV) have been evaluated.